1. Field of the Invention
The present invention relates to a permeable porous die used for molding a synthetic resin by blow molding, vacuum molding, injection molding, rim urethane molding or the like, and a method of molding a synthetic resin by using the porous die.
2. Description of the Related Art
This kind of porous die is generally composed of a thin-walled porous die body with a multiplicity of pores formed therein by laser beam machining, electroforming or other methods, and a reinforcing member for reinforcing the back side of the porous die body. The pores are formed so that the synthetic resin which is to be molded may be sucked under vacuum therethrough from the back side of the porous die body so as to attract it to the surface of the porous die body.
The porous die is likely to be overheated due to the heat of the synthetic resin during molding, so that(the molding cycle the period between the end of one molding and the start of the next molding) is apt to be long. The following measures are therefore taken in order to positively cool the porous die:
(1) A cooling pipe through which a coolant is passed is brought into contact or connected to the back side of the porous die body. PA1 (2) A circulation chamber through which a coolant is passed is provided on the back side of the porous die body with a space therebetween so as to conduct the heat of the porous die body through metal members such as stud bolts and to release the heat into the circulation chamber. PA1 the cooling ability is not enough to effectively shorten the molding cycle, and so on.
Both of the cooling measures (1) and (2), however, are disadvantageous in that there is nonuniformity in the cooling of the porous die body, it is difficult to determine the location of the cooling pipe or the like,
For example, when the applicant of the present invention molded an ABS resin by using the porous die with the cooling measure (2) adopted, it is only to about 6 minutes that the molding cycle was shortened.